Diesel engine aftertreatment system and diesel engine

Abstract

This application relates to the field of diesel engine exhaust gas treatment technology, and provides an aftertreatment system and a diesel engine. The aftertreatment system includes a first oxidation catalytic conversion module located downstream of the diesel engine's exhaust outlet; a particulate filter module located downstream of the first oxidation catalytic conversion module; a selective catalytic reduction module located downstream of the particulate filter module for reducing nitrogen oxides in the exhaust gas discharged from the particulate filter module; an ammonia oxidation catalytic module located downstream of the selective catalytic reduction module for oxidizing ammonia in the exhaust gas discharged from the selective catalytic reduction module; and a second oxidation catalytic conversion module located downstream of the ammonia oxidation catalytic module for decomposing nitrous oxide in the exhaust gas discharged from the ammonia oxidation catalytic module. Using this system can significantly improve exhaust gas treatment efficiency.

Description

Technical Field

[0001] This application relates to the field of diesel engine exhaust gas treatment technology, and in particular to diesel engine aftertreatment systems and diesel engines. Background Technology

[0002] With global environmental issues becoming increasingly prominent, diesel engines, as one of the main power sources, are drawing growing attention to the pollution they cause to the atmosphere. The main pollutants emitted by diesel engines include nitrogen oxides (NOx), particulate matter (PM), hydrocarbons (HC), and carbon monoxide (CO). To meet increasingly stringent emission regulations, diesel engine exhaust aftertreatment technologies have been widely applied and rapidly developed.

[0003] Current diesel engine aftertreatment systems typically employ a series of catalytic converters and filters, forming a multi-stage purification technology that has achieved significant results in reducing traditional pollutants such as NOx and PM. However, under certain operating conditions of diesel engines, aftertreatment systems can easily generate and emit nitrous oxide (N2O). N2O is a potent greenhouse gas with a significant impact on global climate change; its long-term presence in the atmosphere exacerbates the greenhouse effect. Although the concentration of N2O in the original engine emissions is extremely low, its generation in aftertreatment systems, especially under conditions such as low temperatures or excessive reducing agents, can increase significantly, leading to ineffective exhaust gas treatment. Utility Model Content

[0004] Therefore, it is necessary to provide an aftertreatment system and a diesel engine that can improve the exhaust gas treatment effect.

[0005] In a first aspect, this application provides an after-treatment system for a diesel engine, comprising:

[0006] The first oxidation catalytic conversion module is located downstream of the exhaust outlet of the diesel engine and is used to oxidize hydrocarbons, carbon monoxide and nitrogen monoxide in the exhaust gas discharged from the exhaust outlet.

[0007] A particulate filter module, located downstream of the first oxidation catalytic conversion module, is used to capture and / or oxidize particulate matter in the exhaust gas discharged from the first oxidation catalytic conversion module.

[0008] A selective catalytic reduction module, located downstream of the particulate filter module, is used to reduce nitrogen oxides in the exhaust gas discharged from the particulate filter module.

[0009] An ammonia oxidation catalytic module, located downstream of the selective catalytic reduction module, is used to oxidize ammonia in the exhaust gas discharged from the selective catalytic reduction module.

[0010] The second oxidation catalytic conversion module is located downstream of the ammonia oxidation catalytic module and is used to decompose nitrous oxide in the exhaust gas discharged from the ammonia oxidation catalytic module.

[0011] In one embodiment, the exhaust outlet of the diesel engine includes a first exhaust port and a second exhaust port;

[0012] The first oxidation catalytic conversion module is connected to the first exhaust port;

[0013] The second oxidation catalytic conversion module is provided with an exhaust gas preheating inlet and an exhaust gas preheating outlet; one end of the exhaust gas preheating inlet is connected to the second exhaust port, the other end of the exhaust gas preheating inlet is connected to one end of the exhaust gas preheating outlet, and the other end of the exhaust gas preheating outlet is connected to the exhaust gas recirculation pipe of the diesel engine.

[0014] In one embodiment, the second oxidation catalytic conversion module includes:

[0015] The main body housing has an inlet end connected to the ammonia oxidation catalytic module and an outlet end connected to the exhaust tailpipe of the diesel engine;

[0016] The second catalyst support is housed inside the main body shell, and the surface of the second catalyst support is provided with a noble metal layer structure.

[0017] In one embodiment, the second oxidation catalytic conversion module further includes:

[0018] An outer shell is provided to enclose the main body shell, and the inner wall of the outer shell and the outer wall of the main body shell form a preheating cavity;

[0019] Both the exhaust gas preheating inlet and the exhaust gas preheating outlet are located on the outer casing, and both the exhaust gas preheating inlet and the exhaust gas preheating outlet are connected to the preheating cavity.

[0020] In one embodiment, a heat-conducting structure is provided inside the annular cavity, and the heat-conducting structure is disposed on the outer side wall of the main body housing;

[0021] The heat-conducting structure within the annular cavity includes at least one of a finned heat-conducting structure, a ribbed heat-conducting structure, and a heat-storage heat-conducting structure.

[0022] In one embodiment, a spiral heat-conducting pipe is provided inside the main body housing. The inlet end of the spiral heat-conducting pipe passes through the exhaust gas preheating inlet and is sealed to the inlet wall of the exhaust gas preheating inlet. The outlet end of the spiral heat-conducting pipe passes through the exhaust gas preheating outlet and is sealed to the inlet wall of the exhaust gas preheating outlet. The spiral heat-conducting pipe is used to circulate the exhaust gas discharged from the second exhaust port to preheat the catalyst carrier.

[0023] In one embodiment, the spiral heat pipe is arranged to spiral along the inner wall of the main body housing, and the central axis of the spiral heat pipe coincides with the central axis of the main body housing.

[0024] In one embodiment, the body housing is cylindrical or conical; the inlet end and the outlet end are disposed at both ends along the axial direction of the body housing;

[0025] The exhaust gas preheating inlet is located near the inlet end, and the exhaust gas preheating outlet is located near the outlet end.

[0026] In one embodiment, the first oxidation catalytic conversion module includes a first catalyst support, the second oxidation catalytic conversion module includes a second catalyst support, the pore size of the first catalyst support is larger than the pore size of the second catalyst support, and / or the pore density of the first catalyst support is greater than the pore density of the second catalyst support.

[0027] Secondly, this application provides a diesel engine, including the after-treatment system of the diesel engine provided in the first aspect of this application.

[0028] The aforementioned diesel engine aftertreatment system and diesel engine, by adding a second oxidation catalytic conversion module (DOC2) for decomposing nitrous oxide (N2O) at the end of the diesel engine aftertreatment system, can effectively decompose N2O produced by the selective catalytic reduction (SCR) module and the ammonia oxidation catalytic module (ASC). N2O is a strong greenhouse gas with a global warming potential far exceeding that of carbon dioxide. SCR technology, widely used to significantly reduce nitrogen oxide (NOx) emissions, produces N2O as a byproduct under certain operating conditions. This application, by setting up DOC2, decomposes this portion of N2O into harmless nitrogen (N2) and oxygen (O2), thereby achieving effective control of N2O emissions and improving exhaust gas treatment efficiency. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of the after-treatment system of a diesel engine in some embodiments of this application.

[0031] Figure 2 This is a schematic diagram of the structure of the diesel engine aftertreatment system in some other embodiments of this application.

[0032] Figure 3 This is a schematic diagram of the structure of the second oxidation catalytic conversion module in some embodiments of this application.

[0033] Explanation of icon numbers:

[0034] 100. First oxidation catalytic conversion module; 200. Particulate filtration module; 300. Selective catalytic reduction module; 400. Ammonia oxidation catalytic module; 500. Second oxidation catalytic conversion module; 510. Waste gas preheating inlet; 520. Waste gas preheating outlet; 501. Main body shell; 502. Inlet end; 503. Outlet end; 504. Outer shell; 505. Preheating cavity; 600. Waste gas recirculation device. Detailed Implementation

[0035] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0036] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0038] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0039] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0040] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0041] To address the issue of improving exhaust gas treatment efficiency in related technologies, firstly, referring to... Figure 1 One embodiment of this application provides an aftertreatment system for a diesel engine, including a first oxidation catalytic conversion module 100, a particulate filter module 200, a selective catalytic reduction module 300, an ammonia oxidation catalytic module 400, and a second oxidation catalytic conversion module 500.

[0042] The first oxidation catalytic conversion module 100 of this application embodiment is located downstream of the exhaust outlet of the diesel engine, and is used to oxidize hydrocarbons, carbon monoxide and nitric oxide in the exhaust gas discharged from the exhaust outlet.

[0043] The first oxidation catalytic conversion module 100 is located downstream of the engine exhaust outlet. This module 100 can be a diesel oxidation catalytic converter (DOC). The DOC catalyzes the oxidation reaction in the exhaust gas, converting hydrocarbons and carbon monoxide into water and carbon dioxide. Under sufficient oxygen conditions, the DOC can also partially oxidize nitric oxide in the exhaust gas to nitrogen dioxide, providing oxidation conditions for subsequent DPF regeneration.

[0044] The particulate filter module 200 of this application embodiment is located downstream of the first oxidation catalytic conversion module 100, and is used to capture and / or oxidize particulate matter in the exhaust gas discharged from the first oxidation catalytic conversion module 100.

[0045] The particulate filter module 200, located downstream of the first oxidation catalytic conversion module 100 (DOC1), is a core component for treating particulate matter (PM) in diesel engine exhaust. The particulate filter module 200 can be a diesel particulate filter (DPF), which typically employs a wall-flow ceramic or metal fiber structure with alternating open and closed internal channels. When exhaust gas flows through the DPF, it is forced through the porous channel walls, and particulate matter is physically captured on the inner surface of the channels, while the cleaned gas exits from the other end. Furthermore, the DPF can also possess an oxidation function, capable of passively or actively regenerating by using a catalyst or high temperature to oxidize the captured particulate matter into carbon dioxide, thereby restoring its filtration performance. The nitrogen dioxide provided by the DOC acts as a strong oxidant, enabling passive regeneration of the DPF at relatively low temperatures, effectively reducing system energy consumption.

[0046] The selective catalytic reduction module 300 of this embodiment is located downstream of the particulate filter module 200 and is used to reduce nitrogen oxides in the exhaust gas discharged from the particulate filter module 200.

[0047] The selective catalytic reduction module 300 is located downstream of the particulate filter module 200. It can employ an SCR (Selective Catalytic Reduction) catalyst, which removes nitrogen oxides from the exhaust gas through a catalytic reduction reaction. Please refer to [link to relevant documentation]. Figure 1Between the selective catalytic reduction module 300 and the particulate filter module 200, a urea injection module can also be installed to inject an aqueous urea solution into the exhaust pipe. Urea rapidly decomposes into ammonia at high temperatures, which acts as a reducing agent. Under the action of the SCR catalyst, ammonia reacts with NOx in the exhaust gas, converting it into nitrogen and water.

[0048] In one possible implementation, the catalyst of the selective catalytic reduction module 300 may include at least one of a low-temperature vanadium-based catalyst and a copper-iron composite catalyst.

[0049] The ammonia oxidation catalytic module 400 of this application embodiment is located downstream of the selective catalytic reduction module 300, and is used to oxidize the ammonia in the exhaust gas discharged by the selective catalytic reduction module 300.

[0050] The ammonia oxidation catalytic module 400 is located downstream of the selective catalytic reduction module 300. It can use an ammonia slip catalyst (ASC) to treat the ammonia (NH3) that escapes from the SCR module due to incomplete reaction.

[0051] The second oxidation catalytic conversion module 500 of this application embodiment is located downstream of the ammonia oxidation catalytic module 400 and is used to decompose nitrous oxide in the exhaust gas discharged from the ammonia oxidation catalytic module 400.

[0052] In this embodiment, a second oxidation catalytic conversion module 500 (DOC2) is installed downstream of the ASC module. This module employs an oxidation catalytic converter to decompose nitrous oxide in the exhaust gas. Since the SCR catalyst may produce N2O as a byproduct under certain operating conditions and pass through the ASC module, the DOC2 layer of this application can catalyze the decomposition reaction of N2O, converting it into nitrogen and oxygen. The environment in which DOC2 operates is relatively clean exhaust gas after multi-stage purification. Its main function is the decomposition of N2O, ensuring that the entire aftertreatment system effectively controls traditional pollutants such as hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter while significantly reducing N2O emissions.

[0053] Reference Figure 2 In some embodiments, the exhaust outlet of the diesel engine includes a first exhaust port and a second exhaust port.

[0054] The first oxidation catalytic conversion module 100 is connected to the first exhaust port.

[0055] In this embodiment of the application, the exhaust outlet of the diesel engine can be configured to include two independent channels. The first oxidation catalytic conversion module 100 (DOC1) is connected to the first exhaust port, which is the exhaust path. The exhaust gas is discharged after being purified by modules such as DOC1, DPF, SCR, ASC and DOC2 in sequence.

[0056] The second oxidation catalytic conversion module 500 is provided with an exhaust gas preheating inlet 510 and an exhaust gas preheating outlet 520. One end of the exhaust gas preheating inlet 510 is connected to the second exhaust port, and the other end of the exhaust gas preheating inlet 510 is connected to one end of the exhaust gas preheating outlet 520. The other end of the exhaust gas preheating outlet 520 is connected to the exhaust gas recirculation pipe of the diesel engine.

[0057] In this embodiment of the application, the exhaust outlet of the diesel engine includes another independent channel, that is, the second exhaust port is used as the intake point for exhaust gas recirculation. Exhaust gas recirculation (EGR) technology refers to using a portion of the exhaust gas discharged from the engine, reintroducing it into the intake manifold, mixing it with fresh air, and then re-entering the cylinder to participate in combustion.

[0058] In this embodiment, the exhaust gas (EGR exhaust gas) discharged from the second exhaust port can be used to preheat DOC2. The housing of the second oxidation catalytic conversion module 500 (DOC2) can be provided with an exhaust gas preheating inlet 510 and an exhaust gas preheating outlet 520. One end of the exhaust gas preheating inlet 510 is connected to the engine's second exhaust port via a pipe, and the other end is connected to the exhaust gas preheating outlet 520. The exhaust gas preheating outlet 520 is connected to the exhaust gas recirculation pipe of the diesel engine's exhaust gas recirculation device 600. The exhaust gas flow path between the exhaust gas preheating inlet 510 and the exhaust gas preheating outlet 520 is physically isolated from the main exhaust flow path of DOC2. The main exhaust flow path of DOC2 refers to the flow path corresponding to the exhaust gas from upstream modules such as ASC. The exhaust gas flow path between the exhaust gas preheating inlet 510 and the exhaust gas preheating outlet 520 is also physically isolated from the catalyst carrier inside DOC2.

[0059] For example, a portion of the high-temperature EGR exhaust gas from the engine enters the exhaust gas preheating inlet 510 of the DOC2 through the second exhaust port before entering the exhaust gas recirculation pipe. This high-temperature exhaust gas flows through the exhaust gas passages inside the DOC2, heating the catalyst carrier of the DOC2 through heat conduction. After heat exchange, the cooled exhaust gas flows out from the exhaust gas preheating outlet 520 and returns to the exhaust gas recirculation pipe to continue its circulation in the EGR system. This structure achieves efficient utilization of waste heat from exhaust gas to rapidly heat the DOC2 without consuming additional energy, ensuring its effective decomposition of N2O even at low temperatures.

[0060] Furthermore, using EGR exhaust gas to preheat DOC2 not only solves the low-temperature problem of DOC2 but also simultaneously cools the EGR exhaust gas itself. The high-temperature EGR exhaust gas carries a significant amount of heat energy, which is transferred to the catalyst carrier of DOC2, heating it to its effective operating temperature. After heat exchange, the exhaust gas itself experiences a significant temperature reduction. Therefore, the DOC2 preheating exhaust gas channel can function as a partial EGR cooler. It preheats DOC2 while simultaneously performing preliminary cooling of the EGR exhaust gas. This embodiment not only efficiently utilizes waste heat from the exhaust gas, achieving rapid heating of DOC2, but also reduces the workload of the downstream EGR cooler. In some cases, it can even optimize the configuration of the EGR cooling system, thereby improving the overall system's thermal management efficiency and economy.

[0061] In some embodiments, please refer to Figure 3 The second oxidation catalytic conversion module 500 includes a main body housing 501 and a second catalyst carrier. The main body housing 501 has an inlet end 502 connected to the ammonia oxidation catalytic module 400 and an outlet end 503 connected to the exhaust tailpipe of the diesel engine. The exhaust tailpipe of the diesel engine is used to discharge exhaust gas treated by the aftertreatment system to the outside. The second catalyst carrier is housed inside the main body housing 501, and the surface of the second catalyst carrier is provided with a noble metal layer structure. For example, the surface of the second catalyst carrier may be provided with a noble metal Pt layer or a noble metal Pd layer.

[0062] In one embodiment, the second oxidation catalytic conversion module 500 further includes a housing 504.

[0063] The outer shell 504 encloses the main shell 501, and the inner wall of the outer shell 504 and the outer wall of the main shell 501 form a preheating cavity 505, which can be an annular cavity. Both the exhaust gas preheating inlet 510 and the exhaust gas preheating outlet 520 can be located on the outer shell 504, and both are connected to the preheating cavity 505.

[0064] Exemplarily, this application utilizes a double-shell design, with an additional outer shell 504 provided outside the main shell 501 of the DOC2. A preheating cavity 505, which can be annular, is formed between these two shells. The high-temperature EGR exhaust gas does not directly enter the catalyst carrier of the DOC2, but instead enters the sandwich-shaped preheating cavity 505 through an exhaust gas preheating inlet 510 located on the outer shell 504. The exhaust gas flows within the cavity, exchanging heat with the outer wall of the main shell 501, transferring heat to the main shell 501 via heat conduction, thereby heating the catalyst carrier inside the main shell 501. After the heat exchange is complete, the cooled exhaust gas flows out from the exhaust gas preheating outlet 520, also located on the outer shell 504, and returns to the EGR system.

[0065] In one possible implementation, a heat-conducting structure may be provided inside the annular cavity. The heat-conducting structure may be disposed on the outer wall of the main body shell 501. The heat-conducting structure inside the annular cavity may include at least one of a finned heat-conducting structure, a ribbed heat-conducting structure, and a heat-storage heat-conducting structure.

[0066] The finned heat-conducting structure may include multiple metal fins. For example, multiple metal fins may be arranged axially or radially on the outer wall of the main body shell 501. When the EGR exhaust gas flows through the preheating cavity 505, these fins can increase the surface area for heat exchange, allowing heat to be transferred more efficiently from the exhaust gas to the main body shell 501, thereby heating the internal catalyst support. The height, thickness, and spacing of the fins can be optimized according to the flow rate and temperature of the EGR exhaust gas.

[0067] The finned heat conduction structure can include multiple spiral or mesh-like fins, for example, multiple spiral or mesh-like fins can be provided on the outer wall surface of the main body shell 501. These fins not only increase the heat exchange area, but also force the EGR exhaust gas to generate turbulence in the preheating cavity 505, breaking the boundary layer, thereby enhancing the convective heat transfer effect and further improving the heat transfer efficiency.

[0068] The regenerative heat-conducting structure can include a filling layer composed of metal wire mesh, metal foam, or ceramic balls. When high-temperature EGR exhaust gas flows through, these heat regenerators can quickly absorb and store heat. Even if the EGR gas flow is unstable, the heat regenerator can continuously and uniformly transfer heat to the main body shell 501, ensuring a steady increase in the catalyst support temperature. This structure is particularly suitable for intermittent or low-flow preheating conditions.

[0069] In one embodiment, both the exhaust gas preheating inlet 510 and the exhaust gas preheating outlet 520 are disposed on the main body housing 501.

[0070] The main body housing 501 may be provided with a spiral heat-conducting pipe. The inlet end of the spiral heat-conducting pipe passes through the exhaust gas preheating inlet and is sealed to the wall of the exhaust gas preheating inlet. The outlet end of the spiral heat-conducting pipe passes through the exhaust gas preheating outlet and is sealed to the wall of the exhaust gas preheating outlet. The spiral heat-conducting pipe is used to circulate the exhaust gas discharged from the second exhaust port to preheat the catalyst carrier.

[0071] In this embodiment, a spiral heat pipe is installed inside the housing 501 of the second oxidation catalytic conversion module 500 (DOC2). The inlet end of the spiral heat pipe is sealed to the exhaust gas preheating inlet 510 on the housing 501, and its outlet end is sealed to the exhaust gas preheating outlet 520. This allows the high-temperature EGR exhaust gas drawn from the engine's second exhaust port to enter the spiral heat pipe through the exhaust gas preheating inlet 510. The exhaust gas flows along a spiral path inside the pipe, exchanging heat with the surrounding DOC2 housing 501 and catalyst carrier. The exhaust gas transfers the heat it carries to the DOC2 carrier through the pipe wall, achieving preheating. After the heat exchange is complete, the cooled exhaust gas flows out from the exhaust gas preheating outlet 520 and returns to the EGR pipeline.

[0072] In one possible implementation, the spiral heat pipe is arranged to spiral along the inner wall of the main body housing 501, and the central axis of the spiral heat pipe coincides with the central axis of the main body housing 501.

[0073] In this implementation, because the spiral heat pipe is uniformly coiled on the inner wall of the main body shell 501, the heat brought by the EGR exhaust gas can be evenly distributed to the main body shell 501 and the catalyst support inside. Secondly, this structure optimizes the heat exchange efficiency. The spiral heat pipe not only increases the heat exchange area, but its own spiral direction also forces the EGR exhaust gas to form a stable spiral flow inside the pipe, enhancing the convective heat transfer effect.

[0074] In one possible implementation, the main body housing 501 is cylindrical or conical, with an inlet end 502 and an outlet end 503 arranged at both ends along the axial direction of the main body housing 501. The exhaust gas preheating inlet is located near the inlet end 502, and the exhaust gas preheating outlet is located near the outlet end 503.

[0075] In this implementation, by setting the exhaust gas preheating inlet close to the inlet end 502, the EGR exhaust gas with the highest temperature can be concentrated in the area of ​​DOC2 that needs the most heating, namely the inlet side, to achieve the fastest temperature rise.

[0076] In some embodiments, the first oxidation catalytic conversion module 100 includes a first catalyst support, the second oxidation catalytic conversion module 500 includes a second catalyst support, the pore size of the first catalyst support is larger than the pore size of the second catalyst support, and / or the pore density of the first catalyst support is greater than the pore density of the second catalyst support.

[0077] For example, the pore density of the first catalyst support may be 300-400 cpsi (pores per square inch), while the pore density of the second catalyst support may be 400-600 cpsi. Accordingly, the pore size of the DOC1 support is larger than that of the DOC2 support.

[0078] For example, the carrier substrate of the first catalyst support or its surface may also have an alumina or composite oxide layer, or a coating pore structure with a specific micropore size distribution.

[0079] In this embodiment, since DOC1 is located at the front end of the aftertreatment system, the raw, untreated exhaust gas from the engine may contain HC, CO, and NO, and carry a large amount of untreated fuel droplets, carbon deposit precursors, and catalyst poisons such as sulfur and phosphorus from fuel and lubricating oil. Therefore, a larger pore size and lower pore density help reduce the back pressure (i.e., pressure drop) when exhaust gas flows through DOC1, thereby reducing engine pumping losses and improving fuel economy. DOC2 is located at the end of the system, and its main task is to decompose N2O. A higher pore density and smaller pore size mean a larger surface area of ​​catalyst per unit volume, which can provide more active sites to catalyze the decomposition of N2O, thereby achieving higher conversion efficiency at a relatively lower temperature.

[0080] Secondly, embodiments of this application provide a diesel engine that includes an after-treatment system for any of the diesel engines provided in the first aspect above.

[0081] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0082] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An aftertreatment system for a diesel engine, characterized by, The system includes: The first oxidation catalytic conversion module is located downstream of the exhaust outlet of the diesel engine and is used to oxidize hydrocarbons, carbon monoxide and nitrogen monoxide in the exhaust gas discharged from the exhaust outlet. A particulate filter module, located downstream of the first oxidation catalytic conversion module, is used to capture and / or oxidize particulate matter in the exhaust gas discharged from the first oxidation catalytic conversion module. A selective catalytic reduction module, located downstream of the particulate filter module, is used to reduce nitrogen oxides in the exhaust gas discharged from the particulate filter module. An ammonia oxidation catalytic module, located downstream of the selective catalytic reduction module, is used to oxidize ammonia in the exhaust gas discharged from the selective catalytic reduction module. The second oxidation catalytic conversion module is located downstream of the ammonia oxidation catalytic module and is used to decompose nitrous oxide in the exhaust gas discharged from the ammonia oxidation catalytic module.

2. The system of claim 1, wherein, The exhaust outlet of the diesel engine includes a first exhaust port and a second exhaust port. The first oxidation catalytic conversion module is connected to the first exhaust port; The second oxidation catalytic conversion module is provided with an exhaust gas preheating inlet and an exhaust gas preheating outlet; one end of the exhaust gas preheating inlet is connected to the second exhaust port, the other end of the exhaust gas preheating inlet is connected to one end of the exhaust gas preheating outlet, and the other end of the exhaust gas preheating outlet is connected to the exhaust gas recirculation pipe of the diesel engine.

3. The system of claim 2, wherein, The second oxidation catalytic conversion module includes: The main body housing has an inlet end connected to the ammonia oxidation catalytic module and an outlet end connected to the exhaust tailpipe of the diesel engine; The second catalyst support is housed inside the main body shell, and the surface of the second catalyst support is provided with a noble metal layer structure.

4. The system of claim 3, wherein, The second oxidation catalytic conversion module also includes: An outer shell is provided to enclose the main body shell, and the inner wall of the outer shell and the outer wall of the main body shell form a preheating cavity; Both the exhaust gas preheating inlet and the exhaust gas preheating outlet are located on the outer casing, and both the exhaust gas preheating inlet and the exhaust gas preheating outlet are connected to the preheating cavity.

5. The system of claim 4, wherein, The preheating cavity is provided with a heat-conducting structure, which is disposed on the outer wall of the main body shell; The heat-conducting structure within the preheating cavity includes at least one of a finned heat-conducting structure, a ribbed heat-conducting structure, and a heat-storage heat-conducting structure.

6. The system of claim 3, wherein, Both the exhaust gas preheating inlet and the exhaust gas preheating outlet are located on the main body shell; The main body housing is provided with a spiral heat-conducting pipe. The air inlet end of the spiral heat-conducting pipe passes through the exhaust gas preheating inlet and is sealed to the wall of the exhaust gas preheating inlet. The air outlet end of the spiral heat-conducting pipe passes through the exhaust gas preheating outlet and is sealed to the wall of the exhaust gas preheating outlet. The spiral heat-conducting pipe is used to circulate the exhaust gas discharged from the second exhaust port to preheat the catalyst carrier.

7. The system of claim 6, wherein, The spiral heat-conducting tube is arranged to spiral along the inner wall of the main body shell, and the central axis of the spiral heat-conducting tube coincides with the central axis of the main body shell.

8. The system of claim 6, wherein, The main body housing is cylindrical or conical; the inlet end and the outlet end are located at both ends along the axial direction of the main body housing; The exhaust gas preheating inlet is arranged close to the inlet end, and the exhaust gas preheating outlet is arranged close to the outlet end.

9. The system of claim 1, wherein, The first oxidation catalytic conversion module comprises a first catalyst carrier, and the second oxidation catalytic conversion module comprises a second catalyst carrier, the pore size of the first catalyst carrier is greater than the pore size of the second catalyst carrier, and / or, The first catalyst carrier has a greater pore density than the second catalyst carrier.

10. A diesel engine characterized by comprising: The diesel engine comprises the system according to any one of claims 1-9.

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